Dual cassette load lock

ABSTRACT

A workpiece loading interface is included within a workpiece processing system which processes workpieces, typically wafers, in a vacuum. The workpiece loading interface includes two separate chambers. Each chamber may be separately pumped down. Thus, while a first cassette of wafers, from a first chamber is being accessed, a second cassette of wafers may be loaded in the second chamber and the second chamber pumped down. Each chamber is designed to minimize intrusion to a clean room. Thus a door to each chamber has a mechanism which, when opening the door, first moves the door slightly away from an opening in the chamber and then the door is moved down parallel to the chamber. After the door is opened, a cassette of wafers is lowered through the opening in a motion much like a drawbridge. The cassette may be pivoted within the chamber when the position from which wafers are accessed from the cassette differs from the position from which the cassette is lowered out of the chamber.

This application is a continuation of U.S. patent application Ser. No.08/099,983 filed Jul. 30, 1993, now abandoned, which is a continuationof U.S. patent application Ser. No. 07/849,115, filed Mar. 10, 1992, nowabandoned which is a divisional of U.S. patent application Ser. No.07/511,481, filed Apr. 19, 1990, now U.S. Pat. No. 5,186,594.

BACKGROUND

The present invention relates to a front end loading interface used inthe loading of workpieces in semiconductor processing equipment.

Semiconductor processing equipment often has a plurality of chambers inwhich processing occurs. Arm assemblies or other robotic devices aregenerally used to move workpieces, generally wafers from a wafer queuingstation to various chambers for processing. When the processing isfinished the wafer is returned to the queuing station. For an example ofprior art processing equipment, see U.S. Pat. No. 4,715,921 issued toMaher et al. for a Ouad Processor.

Semiconductor processing is typically done in a vacuum. Therefore, awafer queuing station into which is placed a cassette of wafers to beprocessed must be pumped down before the wafers may be accessed. Thissignificantly increases the time the semiconductor processing equipmentis idle while waiting for a cassette of processed wafers to be exchangedfor a cassette of unprocessed wafers and subsequent pumping down of thewafer queuing station.

SUMMARY OF THE INVENTION

In accordance with the preferred embodiment of the present invention, aworkpiece loading interface is presented for inclusion within aworkpiece processing system. The workpiece loading interface includestwo separate chambers. Each chamber may be separately pumped down. Thus,while a first cassette of workpieces, typically wafers, from a firstchamber are being accessed, a second cassette of wafers may be loaded inthe second chamber and the second chamber may then be pumped down. Thiscan significantly increase throughput of wafers through the workpieceprocessing system.

In the preferred embodiment, each chamber is designed to minimizeintrusion to a clean room. Thus a door to each chamber has a mechanismwhich, when opening the door, first moves the door slightly away from anopening in the chamber and then the door is moved down parallel to thechamber. After the door is opened, a cassette of wafers is loweredthrough the opening in a motion much like a drawbridge. The cassette ofwafers is on a support with no side panels, facilitating the replacementof a cassette of processed wafers with a cassette of unprocessed wafersby an automated device. The cassette may be pivoted within the chamberwhen the position from which wafers are accessed from the cassettediffers from the position from which the cassette is lowered out of thechamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of a block diagram of semiconductor processingequipment which includes two cassette load locks in accordance with thepreferred embodiment of the present invention.

FIG. 2 shows a block diagram of a load lock which is part of thesemiconductor processing equipment shown in FIG. 1 in accordance withthe preferred embodiment of the present invention.

FIG. 3 shows a second block diagram of the load lock shown in FIG. 2 inaccordance with the preferred embodiment of the present invention.

FIG. 4 shows another block diagram of the load lock shown in FIG. 2 inaccordance with the preferred embodiment of the present invention.

FIG. 5 is a block diagram of a cassette wafer holder in a positionextended out of the load lock shown in FIG. 2 in accordance with thepreferred embodiment of the present invention.

FIG. 6 is a block diagram of the cassette wafer shown in FIG. 5 in anupright position within the load lock shown in FIG. 2 in accordance withthe preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a top view of semiconductor processing equipment 1 is shown.Semiconductor processing equipment 1 may be used, for example, foretching wafers.

Semiconductor processing equipment 1, includes, for example, aprocessing chamber 3, a processing chamber 4, a processing chamber 5 anda processing chamber 6. A central chamber 2 may be used to temporarilystore wafers on robotic equipment 7 when wafers are being moved to orfrom various of the processing chambers.

Semiconductor processing equipment also includes dual cassette loadlocks. In chamber 8, a wafer cassette 16 holds wafers 10. In chamber 9,a wafer cassette 17 holds wafers 11. Wafer tray 17 pivots around a pivotpoint 15. When wafers 11 from tray 17 are accessed by semiconductorprocessing equipment 1 for processing, wafer tray 17 is flush against agate 13, as shown, and easily accessed by robotic equipment 7 fortransportation into central chamber 2. When wafer tray 17 is ready to beremoved from chamber 9, wafer tray 17 is pivoted back from gate 13 inpreparation for the opening of chamber 9 and removal of wafer tray 17.

Similarly, wafer tray 16 pivots around a pivot point 14. When wafers 10from tray 16 are accessed by semiconductor processing equipment 1 forprocessing, wafer tray 16 is flush against a gate 12 and easily accessedby robotic equipment 7 for transportation into central chamber 2. Whenwafer tray 16 is ready to be removed from chamber 8, wafer tray 16 maybe pivoted back an angle 18 from gate 12, as shown, in preparation forthe opening of chamber 8 and removal of wafer tray 16. In the preferredembodiment, angle 18 is about twenty-one degrees.

Chamber 8 and chamber 9 may be separately and individually pumped down.A vacuum pump 19 is able to provide a vacuum in chamber 8. A vacuum pump20 is able to provide a vacuum in chamber 9. In FIG. 1, vacuum pumps 19and 20 are shown in schematic form. Typically pumps 19 and 20 wouldreside within semiconductor processing equipment 1. Further, while FIG.1 shows two separate pumps, a single pump could be used to separatelyand individually pump down chamber 8 and chamber 9.

FIG. 2 shows a simplified block diagram front view of wafer chamber 8.In the preferred embodiment, the volume of chamber 8 is 46 liters. Adoor 21 is shown in a closed position. Door 21 includes an observationwindow 22. Door 21 is opened and closed using a pneumatic actuatorwithin a rod 24. Magnets in the pneumatic actuator interface attract anouter ring 26. Outer ring 26 is connected to door 21 through an assembly23.

FIG. 3 shows door 21 lowered into an open position. An opening 25, forexample may be fifteen inches high and ten and one half inches wide. Byopening down, the intrusion of door 21 into a clean room may beminimized. In the preferred embodiment the total intrusion is about oneinch.

Once door 21 is lowered, wafer tray 16, on a support structure 43, maythen be lowered out of chamber 8, much like a draw bridge is lowered ata castle entrance. Wafer tray 16 may then be removed and a new wafertray placed upon support structure 43. Support structure 43 is designedwith a hollow bottom so that when door 21 is opened and wafer tray 16 islowered, a laminar airflow may sweep downward through wafers 10.

In FIG. 4, additional detail of the mechanism which controls the openingand shutting door 21 is shown. A side panel 31 of door 21 is connectedto a carriage 30 by a spring 34, a link 36 and a link 35. As controlledby the pneumatic actuator within rod 24, door 21 travels up and downparallel to a rail 50. When being closed, door 21 is stopped by anabutment 32; however, carriage 30 continues upward, expanding spring 34,until a gap 33 is completely closed. While carriage 30 continues movingupward, a pivot 39 connected to link 36, and a pivot 40 connected tolink 35 continue moving upward. However a pivot 37 connected to link 36and a pivot 38 connected to link 35 cause door 21 to move towardscarriage 30. Therefore, as gap 33 is closed, links 35 and 36 translatethe upward motion of carriage 30 into horizontal motion of door 21. Door21 is thus brought snug against, and hence seals chamber 8.

When door 21 is opened, spring 34 compresses causing gap 33 to reappearand links 35 and 36 to straighten, thus moving door 21 horizontally awayfrom chamber 8.

FIGS. 5 and 6 show a block diagram of one possible implementation of anassembly for guiding the lowering and raising of support structure 43.In FIG. 5, support structure 43 and cassette 16 are shown lowered out ofchamber 8. A roller 44 connected to support structure 43 is shownresting on an extension of a cam containing slot 46 within chamber 8. Aroller 45, also connected to support structure 43, is shown at a firstend of a slot track 46.

In FIG. 6, support structure 43 and cassette 16 are shown in the uprightposition within chamber 8. In this position, wafers 10 are horizontaland are stacked so that they are ready to be accessed by semiconductorprocessing equipment 1. When support structure 43 and cassette 16 are inthe upright position, roller 45 is rolled to a second end of slot track46 and roller 44 rests against a stop 49. Stop 49 is an extension of thecam which contains slot 46.

We claim:
 1. In a workpiece processing system comprising multiple vacuumprocessing chambers coupled to a central chamber, a method for loadingworkpieces into the central chamber, comprising the steps of: providingdual workpiece load/unload chambers coupled to the central chamber, eachhaving an opening for receiving workpieces held in a cassette and forforwarding the cassette of workpieces to the central chamber of theworkpiece processing chamber for further transfer to one of the multiplevacuum chambers for processing: providing a cassette support pivotallymounted within each of said load/unload chambers; pivoting each cassettesupport to a first pivot position; operating each cassette support toraise and lower a cassette of workpieces into and out of the opening ofthe respective load/unload chamber when in the first pivot position ofthe cassette support about a horizontal axis, and thereafter pivotingeach cassette to a second pivot position to position the cassette forforwarding of the workpieces to the central chamber from the secondpivot position of the cassette support wherein pivoting occurs about asubstantially vertical axis.
 2. The method of claim 1 wherein thecassette support is vertically oriented and adjacent the opening forreceiving workpieces when in the first pivot position and is verticallyoriented and adjacent the opening for forwarding workpieces when in thesecond pivot position.
 3. The method of claim 2 wherein when operatingeach cassette support to raise and lower, the cassette support lowers toa horizontally oriented position and raises to the vertically orientedposition about a horizontal axis.
 4. The method of claim 1 wherein theangle of pivoting about the substantially vertical axis between thefirst and second pivot position is about 21 degrees.
 5. In a workpieceprocessing system comprising a central chamber connected to at least oneprocessing chamber, a method for loading a workpiece into the centralchamber, comprising the steps of: providing dual workpiece load/unloadchambers each coupled to the central chamber, the dual workpieceload/unload chambers each having a first opening for receiving aworkpiece carrier and a second opening for forwarding a workpiece to thecentral chamber; providing a workpiece carrier support pivotally mountedabout a horizontal axis within each dual workpiece load/unload chamberto receive a workpiece carrier through the first opening; within a firstof the dual workpiece load/unload chambers: pivoting the workpiececarrier support into a first pivot position when a first workpiececarrier is to be received through the first opening, the pivotingoccurring in a first direction; and pivoting the workpiece carriersupport into a second pivot position when a workpiece is to be extractedfrom the first workpiece carrier and forwarded to the central chamber,the pivoting occurring in a second direction that is opposite the firstdirection; and within a second of the dual workpiece load/unloadchambers: pivoting the workpiece carrier support into a first pivotposition when a second workpiece carrier is to be received through thefirst opening, the pivoting occurring in the second direction; andpivoting the workpiece carrier support into a second pivot position whena workpiece is to be extracted from the second workpiece carrier andforwarded to the central chamber, the pivoting occurring in the firstdirection; wherein each pivoting step occurs about a substantiallyvertical axis.
 6. The method of claim 5 wherein the workpiece carriersupport is vertically oriented in both the first and second pivotpositions.
 7. The method of claim 5 wherein the angle of pivoting aboutthe substantially vertical axis between the first and second pivotpositions is about 21 degrees.
 8. In a workpiece processing systemcomprising a central chamber connected to at least one processingchamber, a method for loading a workpiece into the central chamber,comprising the steps of: providing a workpiece load chamber coupled tothe central chamber and having an opening for receiving a workpiececarrier and for forwarding a workpiece from the workpiece carrier to thecentral chamber; providing a single workpiece carrier support mountedfor movement about a horizontal axis and a vertical axis within theworkpiece load chamber for dual movement between lowered and raisedpositions and first and second pivot positions; pivoting the workpiececarrier support to the first pivot position; operating the workpiececarrier support to move between a first lower position to receive theworkpiece carrier and a second raised position to move the receivedworkpiece carrier through the opening and place the workpiece carrierwithin the load chamber when in the first pivot position; and thereafterpivoting the workpiece carrier support to a second pivot position toforward a workpiece from the workpiece carrier to the central chamber;wherein pivoting occurs about a substantially vertical axis.
 9. Themethod of claim 8 wherein the angle of pivoting about the substantiallyvertical axis between the first and second pivot positions is about 21degrees.